1. Field of the Invention
The present invention relates to a video scope utilized in an electronic endoscope system, and, in particular, is directed to treatment for unused circuit patterns on an electronic circuit board incorporated in such a video scope.
2. Description of the Related Art
As is well known, an electronic endoscope system includes a video scope or so-called electronic scope, and a video-signal processing unit or so-called processor, to which the video scope is detachably coupled. The video scope has a rigid manipulating-section, and a flexible conduit section extending from the rigid manipulating-section.
The flexible conduit section of the video scope has a solid-state image sensor, such as a CCD (charge-coupled device) image sensor, provided at a distal end thereof, and is inserted in an organ of a human body for medical examination. To illuminate an object to be sensed by the CCD image sensor, the video scope includes a flexible optical light guide extending therethrough, and the optical light guide terminates at a light-radiating end face at the distal end of the flexible conduit section.
The rigid manipulating-section of the video scope is provided with manual handles for remotely bending a distal end portion of the flexible conduit section, to thereby control the orientation of the solid-state image sensor. Also, various manual switches are provided on the rigid manipulating-section.
The video scope also includes a cable extending from the rigid manipulating-section, and the cable contains electric wires extending from the CCD image sensor and the manual switches. The cable terminates at a connector section which is detachably coupled to the video-signal processing unit. The connector section comprises a housing including a circuit board on which various electronic devices are mounted to drive the CCD image sensor.
As one of the various electronic devices mounted on the circuit board, a digital signal processor (DSP) is known. The DSP is formed as a custom IC package for reading color image signals from the CCD image sensor. The DSP also processes the read color image signals, thereby producing a video signal. The video signal is fed to the video-signal processing unit in which the video signal is further processed to thereby produce a TV video signal, and then the TV video signal is fed to a TV monitor. Namely, the image sensed by the CCD image sensor is reproduced and displayed as a motion picture on a TV monitor.
In the electronic endoscope system, various types of video scope, such as a bronchial scope, an esophageal scope, a gastro scope, a colon scope, etc, are utilized, and thus the video scope is detachably coupled to the video-signal processing unit. Namely, the various types of video scope use the image-signal processing unit in common.
Also, in the electronic endoscope system, various types of video-signal processing unit are utilized. A representative type of video-signal processing unit is constituted such that a TV video signal is produced based on a first type of video signal composed of a luminance signal component, and two color-difference signal components. In another representative type of video-signal processing unit, a TV video signal is produced based on a second type of video signal composed of a luminance signal component and a color signal component. Thus, before the video scope can be utilized in either type of video-signal processing unit, the video scope must be constituted such that both the first type of video signal and the second type of video signal can be produced and output.
A plurality of wiring-patterns is previously arranged and formed on the circuit board such that either the first type of video signal or the second type of video signal can be selectively fed to the video-signal processing unit when the DSP is mounted on the circuit board. Namely, a part of the wiring-patterns is provided for feeding the first type of video signal to the video-signal processing unit, and the remaining part of the wiring-patterns is provided for feeding the second type of video signal to the video-signal processing unit.
Nevertheless, in reality, the first and second types of video signals cannot be directly fed to the video-signal processing unit, because each of the wiring-patterns is cut off at a suitable location. Namely, the first type of video signal cannot be fed to the video-signal processing unit until respective electrical connections are established at the cutoffs in the wiring-patterns for feeding the first type of video signal, and the second type of video signal cannot be fed to the video-signal processing unit until respective electrical connections are established at the cutoffs in the wiring-patterns for feeding the second type of video signal.
Thus, when the first type of video signal is fed to the video-signal processing unit, the wiring-patterns for feeding the second type of video signal remain as unused wiring-patterns on the circuit board. On the other hand, when the second type of video signal is fed to the video-signal processing unit, the wiring-patterns for feeding the first type of video signal remain as unused wiring-patterns on the circuit board. In this case, the unused wiring-patterns are partially supplied with either the first type of video signals or the second type of video signals, and thus may radiate noise because the video signals are similar to high frequency signals. Of course, the radiation of noise should be prevented in that an image reproduced on a TV monitor may be subjected to deterioration.
As an image-reproduction method for reproducing an image on the TV monitor, the NTSC, PAL, and SECAM methods are well known. In these case, it is necessary to regulate operational timing of the DSP in accordance with a series of basic clock pulse having a predetermined frequency according to the introduced image-reproduction method. Namely, the DSP includes various electronic circuits, each of which must be operated in accordance with a series of clock pulses having a given frequency which is derived from the frequency of the basic clock pulse. Thus, so that the DSP can be properly operated, it is necessary to prepare plural kinds of clock pulses having various frequencies which are derived from the frequency of the basic clock pulse.
Accordingly, the circuit board has an oscillator mounted thereon, and the oscillator is constituted so as to produce a series of basic clock pulse having a predetermined frequency according to an introduced image-reproduction method (NTSC, PAL, SECAM). Before the video scope can be adapted to at least two different image-reproduction methods, the circuit board must be provided with two respective oscillators which produce two different types of basic clock pluses having frequencies according to the different image-reproduction methods, and wiring-patterns must be formed on the circuit board such that one of the different types of basic clock pulse can be selectively utilized in accordance with an introduced image-reproduction method.
Thus, when only one of the two oscillators is utilized, a part of the wiring-patterns remains as an unused wiring-pattern on the circuit board. In this case, the unused wiring may be supplied with the basic clock pulse. When the unused wiring-pattern is supplied with the basic clock pulse, i.e. high frequent pulses, the unused wiring-pattern may form a noise-radiation source. As mentioned above the radiation of noise may deteriorate an image reproduced on the TV monitor.